The investigators plan to study whether chronic stress alters noradrenergic systems and whether chronic stress may be responsible for certain age-related defects. To determine the effect of stress on presynaptic norepinephrine biosynthetic systems, they plan to measure the activity of tyrosine hydroxylase. To measure the functional activity of the postsynaptic adrenergic system, they will measure the density and affinity of beta-adrenergic receptors and the activity of catecholamine-stimulated adenylate cyclase. They plan to conduct these experiments in central nervous tissue (tyrosine hydroxycyclase in cerebellum) as well as in peripheral tissues where they plan to correlate receptor changes with cardiac function. In addition, they will attempt to block stress-induced changes pharmaco-logically by administering either propranolol to inhibit the adrenergic responses or naltrexone to block the opiate system.